The present invention relates to a plug, also known as a xe2x80x9ccollarxe2x80x9d or an xe2x80x9canchorxe2x80x9d, such as the ones used for operatively connecting torsion springs to overhead shafts of counterbalancing mechanisms used for garage doors and the like, in order to allow a torque transfer between the torsion spring and the overhead shaft so as to counterbalance such cable operated doors. More particularly, the present invention relates to a plug comprising safety means which interlock with a mating part of the counterbalancing mechanism when tension is applied to the torsional spring, so as to prevent the plug from being readily removed therefrom in order to avoid serious injuries to unexperienced or inadvertent users tampering with the plug when tension is still present in the torsional spring.
It is known in the art that large, vertical, cable operated doors, such as commercial and residential sectional garage doors, usually require counterbalancing mechanisms to counterbalance the weight of the door in order to decrease the force required to open the door and also facilitate its closing from a raised to a lowered position. Large sectional garage doors used in commercial and residential applications may be manually or power operated. In either case, but particularly for manually operated doors, counterbalancing mechanisms have been used for many years to counterbalance the weight of the door and control its opening and closing movements so that one person can easily control the operation of the door. Counterbalancing mechanisms are also advantageous for power operated overhead doors since they reduce the power requirements needed for the motor and they lower the structural strength required for the opening and closing mechanism of the door. In other words, lighter weight, lower cost, door controlling mechanisms may be used if a counterbalancing mechanism is connected to the door to assist it in its opening and closing movements. Furthermore, the provision of a counterbalancing mechanism minimizes the chance of a rapid and uncontrolled closing of the door in the event of failure of one of the components of the door controlling mechanism, which can result in personal injury or damage to property.
It is also known in the art that a widely used type of counterbalancing mechanism generally comprises a pair of spaced apart cable drums connected to flexible cables, each cable being in turn connected to a lower opposite side edge of the garage door. The cable drums are usually mounted on an overhead shaft which is supported above the door opening and is connected to one or more torsion springs which are each fixed to the shaft at one end, and secured to the wall at the other end, so that the cable drums are biased to rotate in a direction which winds the cables onto the drums and counteracts the weight of the door connected to the cables. Generally, conventional counterbalancing mechanisms include two torsion springs which are coaxially mounted onto the overhead shaft and which are opposed to one another. Furthermore, the torsion springs are adjusted by applying tension therein to properly balance the weight of the door so that minimal opening and closing efforts are required, either manually or when motor controlled. The two drums which are used for winding the cables are usually fastened at each opposite end of the overhead shaft and are fixed to the same by means of screws, whose respective ends are in contact with the shaft and exert pressure thereon.
It is also known in the art that conventional, low cost adjustment devices used for the above-mentioned type of counterbalance mechanisms, and widely utilized in the garage door industry, are generally cylindrical xe2x80x9ccollarsxe2x80x9d commonly referred to also as xe2x80x9cplugsxe2x80x9d (or xe2x80x9cconesxe2x80x9d) which are connected to the so-called fixed ends of the torsion springs and are mounted on the aforementioned shaft for adjusting the deflection of the springs to preset the counterbalance force. That is, each torsion spring is usually coaxially mounted onto the overhead shaft and is preferably connected with a stationary plug at one end and a winding plug at the other end. Usually, stationary plugs are connected to a fixed structure, such as for example, a support bracket rigidly mounted to the wall. Moreover, winding plugs are usually removably fixed to the overhead shaft and are used to operatively connect the torsion spring to the overhead shaft so as to allow a torque transfer between the latter two. Hence, the above-mentioned plugs ensure a mechanical connection between each opposite end of the torsional spring and the support or a shaft, depending on whether they are respectively stationary plugs or winding plugs. The winding plugs usually include one or more setscrews which lock the plugs to the shaft to prevent rotation therewith except during adjustment of the spring deflection. The winding plugs also include sockets for receiving winding bars whereby the springs are manually preset, or xe2x80x9cpreloadedxe2x80x9d, by rotating the winding plugs with respect to the shaft using the winding bars and then locking the winding plugs to the shaft with the setscrews.
An important problem associated with the aforementioned type of counterbalancing mechanisms, or with any other type of counterbalancing mechanism which uses similar plugs (also known as xe2x80x9canchorsxe2x80x9d) and tensioning springs is that they constitute a serious injury hazard for unexperienced or inadvertent workers which tamper with said plugs. This arises from the fact that when the cable operated doors are closed, the torsion springs, which are under considerable tension, and the plugs, whether stationary or winding, are readily accessible. It has been experienced that several people, either due to unexperience or inadvertence or any other reason leading to human error, have unscrewed either one of the plugs, or the support bracket for that matter, without taking the necessary precautions, which has resulted in severe personal injuries given the considerable tension present in the torsional spring. The abovedescribed problem is inherent to the plugs known in the art because they are not provided with safety means for preventing such adverse consequences. Therefore, it would be useful to provide a plug which comprises safety means devised so as to prevent the plug from being readily removed when tension is present in the torsional spring.
Another major problem is that none of the types of plugs known in the art provide a simple, quick, reliable, and cost effective way for operatively connecting a torsion spring to an overhead shaft of a counterbalancing mechanism used for garage doors and the like, while further acting as a safety device for said counterbalancing mechanism with which they cooperate. Therefore, it would be useful to provide a simpler, more reliable, easier to use, easier to maintain, safer, quicker, and more cost effective plug which is devised for both operatively connecting a torsion spring to an overhead shaft and for acting also as a safety device for the cable-operated door counterbalancing mechanism with which it cooperates.
The object of the present invention is to provide a xe2x80x9cplugxe2x80x9d, also knows as a xe2x80x9ccollarxe2x80x9d, an xe2x80x9canchorxe2x80x9d, or a xe2x80x9cconexe2x80x9d, which satisfies each of the above-mentioned needs.
More particularly, a first object of the present invention is to provide a plug which comprises safety means devised so as to prevent the plug from being readily removed when tension is present in the torsional spring.
A second object of the present invention is to provide a simpler, more reliable, easier to use, easier to maintain, safer, quicker, and more cost effective plug which is devised for both operatively connecting a torsion spring to an overhead shaft and for acting also as a safety device for the cable-operated door counterbalancing mechanism with which it cooperates.
In accordance with the present invention, the above objects are achieved with a plug mounted at one end of a torsional spring operatively connected to an overhead shaft of a counterbalancing mechanism, wherein the plug comprises projecting interlocking means able to cooperate with corresponding matching means of a mating part of the counterbalancing mechanism, so that when the interlocking means of the plug are inserted into the corresponding matching means and when tension is applied to the torsional spring, the interlocking means interlock with said matching means of the mating part, thereby preventing the plug from being readily removed therefrom.
More particularly, the above objects are achieved by a plug mounted at one end of a torsional spring operatively connected to an overhead shaft of a counterbalancing mechanism, the plug comprising:
a cylindrical collar coaxially mounted onto the overhead shaft, said collar comprising connecting means for connecting the end of the torsional spring onto the collar;
at least one flange projecting longitudinally along the shaft from the collar, said at least one flange being insertable into and cooperable with an aperture of a mating part of the counterbalancing mechanism so as to be interlocked with said aperture when tension is applied to the torsional spring;
wherein said at least one flange comprises a hook-shaped ridge, whereby when tension is applied to the torsional spring, the plug rotates about the overhead shaft so that said ridge interlocks with a corresponding matching notch of the aperture.
Preferably, the plug comprises two flanges, each flange comprising a hook-shaped ridge, whereby when the tension is applied to the torsional spring, the plug rotates about the overhead shaft so that each corresponding ridge interlocks with a corresponding matching notch of each corresponding aperture.
The objects, advantages and other features of the present invention will become more apparent upon reading of the following non-restrictive description of a preferred embodiment thereof, given for the purpose of exemplification only with reference to the accompanying drawings.